A thermal transfer ribbon containing a substrate, a pigmented layer, titanium dioxide, and glass. A multiplicity of glass particles are dispersed within at least one of the layers of the ribbon.
Thermal transfer ribbons are well known to those skilled in the art. Thus, for example, U.S. Pat. No. 5,776,280 discloses a ribbon comprised of a polyester substrate, an intermediate layer of pigmented wax contiguous with the polyester substrate, and a top ink layer.
When a thermal transfer ribbon, such as the thermal transfer ribbon disclosed in U.S. Pat. No. 5,776,280, is used to print on a dark surface, the dark color of the surface being printed sometimes shows through. This xe2x80x9cshow throughxe2x80x9d phenomenon is commercially unacceptable, causing an image which is unattractive. Furthermore, the combination of the color of the surface being printed upon and the color of the image layer being transferred often produces colors not desired.
One solution offered by the prior art was to make the pigmented layer on the ribbon thicker so that more pigment would be transferred and thus would do a better job of hiding the color of the surface being printed upon. However, increasing the thickness of the pigmented layer often produced ribbons with poor adhesion of such layer to the polyester, flaking of the pigmented layer, and consequent poor print quality.
Another solution offered by the prior art was to maintain the thickness of the pigmented layer but to increase the concentration of pigment within such layer. This solution, although it often led to a more opaque printed job, also often produced a printed layer which was not durable, suffering from chalkiness; such a layer often was easily abraded.
It is an object of this invention to provide a novel thermal transfer ribbon which produces a printed product which is economical, durable, substantially non-flaking, and substantially opaque.
In accordance with this invention, there is a provided a thermal transfer ribbon with an effective contrast ratio of at least about 87 percent and a brightness of at least about 70, wherein said thermal transfer ribbon is comprised at least one coating disposed on such substrate, and wherein said coating is comprised of from about 45 to about 90 weight percent of titania with a particle size of from about 0.1 to about 1.0 microns and from about 0.05 to about 20 weight percent of glass particles with a particle size smaller than about 15 microns.